Neurofilament Light Disordered Tail Mutations Reshape Its Self-Assembled Network Structure

Area of Science:

• Biochemistry and Molecular Biology
• Neuroscience
• Structural Biology

Background:

• Intrinsically disordered proteins (IDPs) and their intrinsically disordered regions (IDRs) perform crucial cellular roles without stable structures, challenging traditional structure-function paradigms.
• Neurofilament-light (NFL) proteins, featuring IDRs in their tail domains, self-assemble into filaments that form nematic hydrogels essential for neuronal integrity.
• Mutations in NFL are associated with Charcot-Marie-Tooth (CMT) disease, but the underlying molecular mechanisms remain poorly understood.

Purpose of the Study:

• To investigate the molecular effects of CMT-associated mutations in NFL tail domains.
• To elucidate how sequence changes in IDRs influence protein network organization and function.
• To provide structural insights into IDR-related pathologies like CMT disease.

Main Methods:

• Combined small-angle X-ray scattering (SAXS) for structural analysis.
• Microscopy techniques to visualize filament assembly and network structure.
• Deep-learning based conformational analysis to study sequence-dependent ensembles.

Main Results:

• CMT-associated NFL tail mutations lead to hydrogel compaction and altered water retention dynamics.
• Mutations disrupt filament nematic order by inducing microdomain formation within the hydrogel.
• Sequence changes shift conformational ensembles, causing macroscopic network rearrangements.

Conclusions:

• Subtle sequence alterations in intrinsically disordered regions (IDRs) significantly modulate protein network organization and function.
• NFL tail mutations disrupt neuronal hydrogel properties, offering a molecular basis for CMT disease.
• This study highlights the critical role of IDRs in maintaining neuronal integrity and provides insights into IDR-related neurodegenerative diseases.